Diabetic nephropathy (DN), which is characterized by renal
fibrosis, is a major complication of diabetes, a disease that afflicted more than 460 million people worldwide in 2019. Pyroptosis is an essential signaling pathway in DN-related
injuries, such as renal
fibrosis.
Pyrroloquinoline quinone (PQQ) is a naturally occurring bioactive compound that protects human kidney 2 (HK-2) cells from oxidative stress-induced damage caused by high
glucose concentrations. However, the nature and underlying mechanism of the effect of PQQ on DN-related renal
fibrosis remains unclear. In this study, we evaluated whether PQQ has potential protective effects against renal
fibrosis due to DN by establishing
type 1 diabetes in mice via
streptozotocin treatment and then inhibiting their pyroptosis signaling pathway. We found that compared to control mice, the area of renal
fibrosis and injury were significantly increased in diabetic mice, and this was accompanied by increased levels of expression of
collagen Ⅰ and
transforming growth factor-β1; increased concentrations of the inflammatory
cytokines,
interleukin (IL)-1β,
IL-6, and
tumor necrosis factor-α; and activation of the pyroptosis pathway components
nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1, IL-1β, and
IL-18. All of these changes were reversed by PQQ treatment. Analogously, we treated cultured HK-2 cells with a high concentration of
glucose (35 mmol/L), which caused these cells to exhibit significantly increased concentrations of
reactive oxygen species (ROS), phosphorylated (p)-
nuclear factor kappa B (NF-κB), p-IkappaB, NLRP3, caspase-1, IL-1β, and
IL-18, and the loss of mitochondrial transmembrane potential. However, PQQ treatment significantly blunted these effects. In conclusion, in this study we demonstrated that PQQ attenuates renal
fibrosis by alleviating
mitochondrial dysfunction, reducing ROS production, and inhibiting the activation of the NF-κB/pyroptosis pathway under conditions of DN and
hyperglycemia.